In other words, 821 nails is 0.0000101164 times the length of I-80, and the length of I-80 is 98,849.4 times that amount.

(a.k.a. Interstate 80, a.k.a. Keystone Shortway) (net length)
Interstate 80, crosses the continent of North America from Teaneck, New Jersey to San Francisco, California and covers a total length of 81,155,400 nails. A 1,049,870 nails stretch between mile marker 318 in Grand Island, Nebraska and mile marker 390 in Lincoln, Nebraska is the longest straight path in the US Interstate system.

It's about one-one-hundred-fifty-thousandth as long as The Great Wall of China (wall only).

In other words, 821 nails is 0.000007496 times the length of The Great Wall of China (wall only), and the length of The Great Wall of China (wall only) is 133,400 times that amount.

(长城, 長城, Chángchéng, a.k.a. 万里长城, 萬里長城, Wànlǐ Chángchéng) (a.k.a. "The long wall of 10,000 Li") (from Shanhaiguan through Lop Nur, China) (wall segments only)The Great Wall of China has total wall segment length of 109,500 nails. Built and maintained in multiple sections over about eleven centuries, the Great Wall is currently suffering the effects of erosion, especially in the older sections made primarily out of mud.

It's about one-one-hundred-fifty-thousandth as long as The Amazon River.

In other words, 821 nails is 0.000007289 times the length of The Amazon River, and the length of The Amazon River is 137,200 times that amount.

(from Nevado Mismi, Arequipa, Peru through near Marajó, Brazil) (approximate distance)The Amazon River has an approximate distance of 112,600,000 nails. Although by most measures it is the largest and one of the most significant rivers in the world, the region surrounding the Amazon is mostly sparsely populated and the river itself has no bridges across it at any point.

It's about one-two-hundred-thousandth as long as The Great Wall of China (total).

In other words, 821 nails is 0.0000053 times the length of The Great Wall of China (total), and the length of The Great Wall of China (total) is 189,000 times that amount.

(长城, 長城, Chángchéng, a.k.a. 万里长城, 萬里長城, Wànlǐ Chángchéng) (a.k.a. "The long wall of 10,000 Li") (from Shanhaiguan through Lop Nur, China) (total length, all branches)The Great Wall of China, including all branches and trenches, is 155,000,000 nails. Built and maintained in multiple sections over about eleven centuries, the Great Wall is currently suffering the effects of erosion, especially in the older sections made primarily out of mud.